The present invention is in the field of backplane communication and pertains more particularly to a fiber-optics backplane for a scalable router.
In the general state of the art of electrical and electronic systems housed in cabinets (often termed chassis), there are typically inputs and outputs to the system, facilitated by connection of communication links of various sorts, over which signals are received and sent. There are also numerous situations wherein groups of components in a chassis have to be connected to and communicate with other groups of components intemally. Data routers in packet networks, such as the well-known Internet, are a good example. In description in this specification a data router is used as a specific example of such a situation, and the present invention in several aspects is applicable to such routers.
Transmission of network data traffic is accomplished with the use of data routers as introduced above. A physical data routing machine typically consists of a processing unit or multiple units which are housed in a chassis and which communicate with each other and with other data routing machines.
In prior art, one method for achieving communication between processing units in a single chassis, such as in a data router, involves the use of an electrical backplane. When communication between multiple chassis is required, the electrical backplanes of the chassis have been connected by cables. The electrical backplane is commonly implemented as a printed circuit board assembly which provides electrical connectivity between processing units.
Noting that it may sometimes be desirable to communicate at backplane level between elements that are not closely physically associated, such as between elements that may be mounted in separate physical electronic cabinets, there is a potential problem with electrical backplanes. When an electrical signal is transmitted over relatively long distances, for example, deterioration of the signal may occur for any of several reasons. For example, longer signal paths necessarily present additional resistance. Also, longer paths present additional opportunity for interference. Therefore, in order to transmit clean signals in systems utilizing electrical backplanes the elements in communication must be in relatively close physical proximity to one another, such as in the same cabinet.
Another drawback to electrical backplane boards is that they are relatively difficult to service. One reason is that the conductors for the electrical signals are typically patterned on the board, and individual conductors (signal paths) cannot be separately serviced In many cases the backplane boards are also hardwired to other components. Because any change or repair is normally via a replacement of the entire backplane, the system containing the electrical backplane is generally out of service during any backplane service.
What is clearly needed is an apparatus and method enabling cleaner data signal transmission between router processing units while at the same time facilitating easier manufacturing and off-line servicing of backplane assemblies.
In a preferred embodiment of the present invention a modular and adjustable backplane assembly to provide backplane communication between a first signal interface to a first set of components in a cabinet and a second signal interface to second set of components in the same cabinet is provided, comprising a first portion mounting a third signal interface configured to engage the first signal interface, a second portion mounting a fourth signal interface configured to engage the second signal interface, an adjustment mechanism allowing relative movement between the first and second portions, thereby between the third and fourth signal interfaces, while preserving the modularity of the backplane assembly, and a signal conductor assembly engaging the third and fourth signal interfaces to communicate signals between the first set of components and the second set of components.
In a preferred embodiment the cabinet houses elements of a packet router, and the first and second sets of components are router cards. In some embodiments the first and second signal interfaces are groups of connectors for connecting signal conductors to individual ones of the cards in the first and second sets of router cards. Further, the first and second signal interfaces may be first and second connectors to printed circuit boards (PCBs) that are in turn connected to the first and second set of components.
In some cases the third and fourth signal interfaces comprise fiber-optic connectors, and the signal conductor assembly comprises one or more fiber-optic fibers having end-connectors for engaging the fiber-optic connectors. The fibers may comprise one or more bundles, ribbons or cables.
In some cases the third and fourth signal interfaces comprise electrical connectors, and the signal conductor assembly comprises one or more cables of electrical conductors having end connectors to engage the electrical connectors. Also in some cases the signal conductor assembly comprises a cable of electrical conductors having end-connectors to engage the electrical connectors at the PCBs.
In some embodiments of the backplane assembly the adjustment mechanism comprises telescopic engagement elements allowing adjustment of separation between the first and second portions. The re may further be a locking mechanism for securing the telescoping first and second portions after adjustment to engage the first and second interfaces.
In other embodiments the adjustment mechanism further comprises first locating elements in the immediate area of each of the first and second signal interfaces, and compatible locating elements in the immediate area of the third and fourth signal interfaces, to physically locate the first and second portions in assembly to the cabinet to engage the first and third and the second and fourth signal interfaces. The locating elements may comprise male and female elements for constraining engagement position.
In another aspect of the invention a method for connecting a first signal interface connected to a first set of components and a second signal interface connected to a second set of components in a cabinet, comprising the steps of (a) preparing a modular and adjustable backplane assembly comprising a first portion mounting a third signal interface configured to engage the first signal interface, a second portion mounting a fourth signal interface configured to engage the second signal interface, an adjustment mechanism allowing relative movement between the first and second portions, thereby between the third and fourth signal interfaces, while preserving the modularity of the backplane assembly, and a signal conductor assembly engaging the third and fourth signal interfaces to communicate signals between the first set of components and the second set of components; and (b) assembling the modular backplane assembly to the cabinet, with the third signal interface engaging the first, and the fourth signal interface engaging the second, the adjustment mechanism allowing the third and fourth signal interfaces to assume a proper separation distance to accomplish engagement of the signal interfaces.
In some embodiments the cabinet houses elements of a packet router, and the first and second sets of components are router cards. In these embodiments the first and second signal interfaces may be groups of connectors for connecting signal conductors to individual ones of the cards in the first and second sets of router cards. Also in some embodiments the first and second signal interfaces may be first and second connectors to printed circuit boards (PCBs) that are in turn connected to the first and second set of components. Further, in some embodiments the third and fourth signal interfaces comprise fiber-optic connectors, and the signal conductor assembly comprises one or more fiber-optic fibers having end-connectors for engaging the fiber-optic connectors. The fibers may comprise one or more bundles, ribbons or cables. In some cases the third and fourth signal interfaces comprise electrical connectors, and the signal conductor assembly comprises one or more cables of electrical conductors having end connectors to engage the electrical connectors. Also in some cases the signal conductor assembly comprises a cable of electrical conductors having end-connectors to engage the electrical connectors at the PCBs.
In some embodiments the adjustment mechanism comprises telescopic engagement elements allowing adjustment of separation between the first and second portions, and there may further be a locking mechanism for securing the telescoping first and second portions after adjustment to engage the first and second interfaces. In addition there may be first locating elements in the immediate area of each of the first and second signal interfaces, and compatible locating elements in the immediate area of the third and fourth signal interfaces, to physically locate the first and second portions in assembly to the cabinet to engage the first and third and the second and fourth signal interfaces. The locating elements may comprise male and female elements for constraining engagement position.
In another aspect there may be a fifth signal interface connected to one or both of the third and fourth signal interfaces, the fifth signal interface placed on the backplane assembly to be accessible with the backplane assembly mounted to the cabinet, to facilitate connection of the backplane assembly to a second backplane assembly having a fifth signal interface and assembled to a second cabinet, thereby providing signal communication between components in the first cabinet and the second cabinet. The fifth signal interface may be a connector for connecting one or more signal conductors, and may comprise a fiber-optic connector compatible with a mating connector for one or more fiber-optic fibers between the backplane assemblies. The fiber-optic fibers can be in one or more ribbons or cables.
In yet another embodiment the fifth signal interface is an electrical connector compatible with a mating connector of an electrical cable between the backplane assemblies.
In embodiments of the invention taught in enabling detail below, for the first time an adjustable cabinet backplane is provided to the art, in which regions of the backplane may be positioned in assembly according to the positions of elements of the cabinet to which the backplane is to be assembled. Also for the first time an ability to interconnect elements in each cabinet at the backplane level is provided.